Combined use of Nassarius reticulatus imposex and statolith age determination for tracking temporal evolution of TBT pollution in the NW Portuguese continental shelf.

Spatial and temporal trends of tributyltin (TBT) pollution on the northern continental shelf of Portugal (5-34 m depth) were assessed using Nassarius reticulatus as a bioindicator. Imposex levels were determined in 2006 and 2010, and integrated with age readings from statoliths for a better chronological analysis of the data. Females affected with imposex were detected in 84% of the sites surveyed in 2006, with levels higher than the Ecological Quality Objective (EcoQO) set by the OSPAR Commission for N. reticulatus (VDSI < 0.3) in approximately half of those sites. In 2010, imposex was only detected in 20% of the surveyed sites and, when detected, the VDSI were lower than the EcoQO, except for one location. The comparison between the current results and the levels previously reported for 2004 and 2005 in the same offshore area evidences a clear decline of imposex in 2010 that confirms the efficacy of Regulation (EC) No. 782/2003 and the IMO AFS-Convention (entered into force in 2003 and 2008, respectively). Moreover, the age of the whelks used in the monitoring is estimated in 3-5 years, indicating that actual TBT water contamination in 2010 may in fact be lower than that extrapolated from the imposex levels. We conclude that the legislation was indeed very effective in reducing TBT pollution in the NW Portuguese continental shelf, not only in terms of the magnitude but also in terms of fast field repercussion.

Assessment of digenean parasitism in Nassarius reticulatus (L.) along the Portuguese coast: evaluation of possible impacts on reproduction and imposex expression.

A survey was performed between June and September 2006 along the Portuguese coast to assess the prevalence of digenean parasitism in the netted whelk Nassarius reticulatus, a bioindicator of tributyltin (TBT) pollution. It was also intended to evaluate the effect of parasites on the reproduction of this gastropod species and their interference on the development of imposex (the superimposition of male characters onto prosobranch females) and male penis, based on field data. Five digenean species (Lepocreadium album, Gynaecotyla longiintestinata, Himasthla quissetensis, Diphtherostomum brusinae, and Cardiocephalus longicollis), plus 1 unidentified species, were found to infect N. reticulatus. Parasitism was spread along the Portuguese coast, but the higher values of prevalence were found in sheltered inshore areas where up to 67.4% of the animals were affected per sampling station. Parasitism has a castrating impact on the whelks and a reducing effect on male penis size, which causes serious disorders in the reproduction of N. reticulatus and may have an important impact in its population dynamics. However, no relationship between imposex severity and parasite infestation was found.

Temporal evolution of imposex in Nassarius reticulatus (L.) along the Portuguese coast: the efficacy of EC regulation 782/2003.

Imposex levels in Nassarius reticulatus (L.) were determined in 44 sites along the Portuguese coast in 2006 in order to describe spatial and temporal trends of TBT pollution in the area. The percentage of females with imposex across sites varied between 20 and 100, denoting the extent of this phenomenon throughout the Portuguese coast. The mean female penis length per site varied between 0.0-8.0 mm and the relative penis length index (mean female penis length x 100/mean male penis length) attained a maximum value of 92%, i.e., female penis never surpasses the size of the male penis but nevertheless it can almost approach the male dimensions. The vas deferens sequence index ranged from 0.2 to 4.5 and the oviduct convolution index varied between 0.0 and 1.3 across stations. The penis growth, the vas deferens development and the oviduct convolution were all correlated and constitute visible signs of a global virilisation progression in females in response to the proximity of harbours that constitute the main TBT pollution sources. The results indicate that about 95% of the surveyed sites were still exposed to TBT water concentrations above the OSPAR Environmental Assessment Criteria. Nevertheless, signs of recovery are shown by the significant reduction of VDSI levels in 2006 in comparison to 2003, which points to the efficacy of the EC Regulation 782/2003 in reducing TBT pollution levels in the Portuguese coast.

Inshore/offshore gradients of imposex and organotin contamination in Nassarius reticulatus (L.) along the Portuguese coast.

Imposex and organotin (OT) tissue contamination of the netted whelk Nassarius reticulatus (L.) were assessed in the continental shelves around the main estuaries of the central coast of Portugal (Lisbon: Tagus estuary; Setúbal: Sado estuary) and the main coastal lagoon in the Southern of Portugal (Faro: Ria Formosa). Pollution levels were higher in areas of more intense boat traffic and shipyard activities and imposex showed a clear decreasing gradient from the estuaries to the offshore, in relation to a similar gradient of tissue contamination by tributyltin. Remarkably, imposex was extensively spread over the adjacent continental shelves of Tagus and Sado estuaries. The current work shows that TBT pollution is undoubtedly a matter of concern not only for the above estuaries where harbours are implanted but also for the adjacent continental shelves, regardless the massive dilution of contaminants that may occur in these deeper areas.

Assessment of inshore/offshore tributyltin pollution gradients in the northwest Portugal continental shelf using Nassarius reticulatus as a bioindicator.

Imposex and organotin tissue contamination were assessed in Nassarius reticulatus (L.) populations in the northwest Portuguese continental shelf between 2002 and 2005 over an area of 735 km2, involving 366 sampling sites. The objective was to evaluate the dispersion of tributyltin (TBT) from inshore sources inside the Ria de Aveiro estuary into the adjacent deeper sea and to assess endocrine disruption in the netted whelk N. reticulatus, using imposex as a biomarker. The highest levels of TBT tissue contamination and imposex were found in the whelks inside the Ria de Aveiro, and these declined logarithmically with distance from the mouth of this estuary. Remarkably, we found that offshore populations were also extensively affected: TBT (the dominant organotin) tissue concentration was above the detection limits at all sites where whelks were analyzed (12-356 ng TBT-Sn/g dry wt), and imposex occurred at 80% of the sampling stations, with relatively high values at some sites from the deepest area surveyed. This work shows clearly that TBT pollution is not restricted to the Ria de Aveiro but affects a significant part of the adjacent continental shelf as well. The ecological impacts of TBT pollution on offshore ecosystems are discussed.